In the field of biometry, there are various techniques for validating the identity of a person. These techniques include facial recognition, fingerprint technology, iris scanning and retinal scanning. Facial recognition and fingerprint technology are generally well recognized in biometry but have inherent inaccuracies. With facial recognition, key indices of facial morphology are recorded digitally and stored on a database for future comparison. Weight loss or gain, changes in facial hair, cosmetic surgery or particular clothing worn for religious reasons that may partially cover the face, can render the technology unreliable. Facial recognition has at best a 95% reliability for identifying uniqueness.
Fingerprint technology has a long history in assisting with the solving of crime. Digital recording of fingerprint data relies on recording the miniature of fingerprints of subjects that may be kept on a database for later comparison. Fingerprint recognition becomes unreliable with five percent of the population having either congenitally blurred fingerprints or worn finger pads resulting from manual labor. These factors make fingerprint scanning potentially unreliable for a significant number of subjects when dealing with a large population. Civil libertarians are resistant to the holding and possible sharing of a database that can incriminate. Fingerprints can be obtained without consent and reproduced without the knowledge of the “owner” of the data.
Iris scanning has been available for around ten (10) years and involves—recording by means of photography some 250 or so features from the iris of the eye. The iris of the eye surrounds the central pupil, designed to expand and contract with variation in the light entering the pupil. As the pupil expands and contracts with variation in light levels or drugs of a class that may have a parasympathomimetic, parasympatholytic or sympathomimetic activity on the iris sphincter pupillae or dilator fibres, so then will the data change for the iris features. Iris data will also change as the pupil expands or contracts with variation in circulating adrenalin. This has limitations in the use of iris recognition systems, particularly out-doors in photopic conditions or indoors in scotopic conditions. Iris recognition performs reliably only in controlled illumination. Further, some racial groups have a perfectly smooth pigmented surface to the anterior iris surface lacking the Crypts of Fuch or iris naevi. Examples include a significant number of the indigenous Australians, New Zealand Maoris and Hawaiians. This causes an iris recognition system to be less reliable when screening such irides. The most optimistic of claims for iris recognition systems are around 94 to 99 percent accuracy—so for every 100 scans there will be at least one false match. This poses a significant problem for managing large databases where for example in a database of 60 million each person's scan will match 600,000 records in the database making it impossible to prevent someone claiming multiple identities. An iris scan can be obtained from up to one (1) meter away from the eye and thus there is opportunity to obtain data without consent.
With retinal scanning, the features of the optic nerve and retinal blood vessels are imaged to provide an excellent marker of uniqueness. However, acquiring this image requires clear media of the eye namely the cornea, lens and vitreous and a reasonable pupil size, typically at least 2.75 mm. This presents a problem when scanning eyes over the age of 60 years where, in the normal process of ageing, the clarity of the crystalline lens declines to ultimately form a cataract and the pupil becomes relatively smaller, commonly less than 2.5 mm, thus making the capture of a reliable image difficult and at times impossible. Whilst retinal scanning has high accuracy, capturing the data reliably poses a problem particularly in older age groups.